Method of making fabric



Patented May 9, 1939 John Blanchard Miles,

Jr., Wilmington, Del., as-' signor to E. I. du Pont de Nemours &Company, Wilmington, Del.. a corporation of Delaware No Drawing.

Application June 28, 1938, Serial No. 216,409. In Germany February 10,1938 6 Claims.

This invention relates to knitted fabrics, and more particularly to thepreparation of high quality hosiery from synthetic linear condensationpolyamide yarns.

An object of this invention is to provide an improved commercial processfor making hosiery from synthetic linear condensation polyamide yarns.Another object is to prepare a dyed polyamide stocking by an improvedcommercial process. Other objects will become apparent as thedescription proceeds.

I These objects are accomplished by subjecting a stocking or stockingfabric knitted from a synthetic polyamide yarn to a board-settingoperation, followed by the steps of scouring, dyeing and reboarding, aswell as by other operations that may desired, e. g., finishing andrinsing.

The board setting operation which is effected after knitting and beforesubjecting the fabric to any. other treatment involving hot, wetconditions, such as scouring, dyeing or rinsing, consists in positioningthe stocking on a smooth, rigid form of such a shape that the stockingwill become slightly tensioned when it is subjected to the hot, wetaction of a non-solvent swelling agent for the polyamide yarns,preferably hot water or saturated (wet) steam, for a time suflicient toset the yarn in a substantially permanent form. In other words, boardsetting fixes the character of the needle and sinker loops in thestocking, as formed by the knitting machine. For convenience, this boardsetting operation prior to any hot, wet treatment of the fabric willhereinafter be referred to as pre-boarding.

The synthetic linear condensation polyamide filaments or fibers used inthisvinvention are described by W. H. Carothers in Patents Nos.2,071,250, 2,071,251 and 2,071,253. In copending application Serial No.125,886, filed February 15, 1937, Carothers has shown that his fibers,unlike other artificial fibers, yield knitted stockings fully equal toand under most conditions superior to natural silk stockings inelasticity, clinging properties, freedom from bagginess, and wearingqualities. He attributes these advantages in large measure to thesurprisingly good bending elasticity" of the fibers.

The preferred commercial process for dyeing stockings, e. g. silkstockings, comprises rapidly agitating the stockings contained in openmesh bags in a hot, aqueous dye bath. Ifthis procedure is applied topolyamide stockings comprising synthetic polyamide fibers, the stockingsdevelop persistent wrinkles unless special precautions are taken. Thereason this difliculty is encountered is that the hot scouring, dyeingor rinsing treatment applied before boarding tends to set in thestockings any wrinkles which are present as well as to set the yarn inthe form of needle and sinker loops, and that it is difiicult to removethese wrinkles by subsequent boarding. In this respect the syntheticpolyamide fabrics differ radically from silk, rayon or other syntheticfabrics. Silk and cellulosic fabrics canbe made to assume a given formby wetting, followed by drying while held in the desired shape. One suchtreatment does not prevent the fabric from assuming a new shape impartedby a secondsimilar treatment. With these fabrics this action is easilyreversible and setting takes place during the drying step. With thesynthetic polyamide fabrics, on the other hand, setting is accomplishedby contact with hot water, steam or other mild swelling agents for thepolyamide yarns even in the absence of subsequent drying, and setting isnot easily reversible. In other words, the effects of a settingtreatment on a polyamide fabric cannot be overcome by a second settingtreatment of equal severity. However, if the second treatment is mademore severe, e. g., by means of a wet treatment at a higher temperatureand/or by a much more prolonged treatment, the fabric can be set inanother form quite successfully. Obviously, it is desirable to avoidthese drastic or time consuming resetting operations.

In practicing the present invention, in order to eliminate thisdifliculty of resetting, the stocking is first subjected to settingconditions in substantially its ultimate form by the pre-boardingoperation. By pre-boarding the stocking for relatively short periods andat easily attainable temperatures, it is possible to subject thestocking to any common commercial scouring, dyeing or rinsing operationswithout forming persistent wrinkles. v

Also, in practicing this invention, the knitted synthetic linearcondensation polyamide stockings before being subjected to any hot, wettreatment are carefully fitted on to a non-yielding boarding form whichholds the stocking in approximately its desired shape. The stocking maybe placed on the form wet or dry. If it is placed on the form dry, it ispreferable to wet it before the setting treatment and this canconveniently be done by dipping or spraying. While on this form thestocking isgiven a board setting treatment. As already indicated, thisconsists in a hot, wet treatment with the liquid or vapor of anon-solvent swelling agent for the polyamide yarn. The degree ofswelling produced by the preferred setting agents, e. g., water and thelower aliphatic alcohols, is small, usually in the range of 1% to 6%.The time of treatment required to secure adequate setting of the fabricwill depend upon the temperature and the nature of the setting agentemployed. The preferred treatment consists in subjecting the stocking tothe action of hot water or saturated steam at a temperature between 95and 110 C. for a time ranging from about one to fifteen minutes,depending upon the temperature. For example, a one minute treatment withsaturated steam at 100 C. is approximately equivalent to five minutestreatment with water at 95 C. The degree of setting in a given time isroughly a linear function of the temperature.

Since pre-boarding is the first hot, wet treatment applied to thepolyamide stocking fabric, it determines to a large degree the permanentcharacteristics of the stocking. In other words, preboarding is acontrolling setting treatment, the effects of which are not destroyed bythe normal treatments subsequently applied to the stocking.

After the pre-boarding step, the knitted fabric, for example a stocking,is scoured, e. g., to remove finish, being then dyed upon beingsubjected to a bath containing a suitable dye, both the dyeing andscouring operations normally taking place at an elevated temperature, e.g., 80 to 100 C. The fabric is rinsed, treated with a suitable finish,and is wrung to remove excess liquid. During the treatments subsequentto pre-boarding, the fabric will acquire superficial wrinkles, i. e.,wrinkles which may easily be removed, and for this reason, the fabric issubjected to a boarding operation, in which the fabric is placed over anon-yielding boarding form, wet with water if desired or treated withsteam, and in any event dried on the form whereby to acquire a neat,unwrinkled appearance. This step is called reboarding for convenienceand is intended to include within its scope any equivalent treatment,such as ironing, which will eliminate distortions or wrinklestemporarily induced in the fabric subsequent to pre-boarding.

Stockings produced in accordance with this invention as indicated aboveare substantially wrinkle free and present an excellent appearance. Thestockings are characterized by excellent loop formation and elasticproperties since the yarn has been set in the loop formation before ithas had much opportunity to slip and slide in an effort to straightenout. The stockings of this invention can also be laundered and driedrepeatedly without materially destroying their good appearance.

The following examples illustrate my invention in greater detail. Theyarns used in these- Following twisting, theseyarns are exposed on pirnsto air at 76 C. and 78% relative humidity for one hour to reduce theliveliness of the twist. This procedure makes it possible to perform thesubsequent operations of coming and knitting successfully in spite ofthe high twist in the yarn.

These yarns are then knit on a full-fashionedhosiery machine todimensions as determined by trial. The yarn, in knitting, is passed overa wick or roller moistened with water or through water in thetraditional manner. The 69 denier yarn is used for the welt, heel, sole,and splices. The 45 denier yarn is used for the leg and instep, whichare knit with a three-carrier setup. The 135 denier yarn is used for thetoe. Following knitting, the stocking is looped and seamed in thecustomary manner. The completed, undyed stocking is now moistened withwater at 20 C. and is carefully fitted over a metal hosiery boardingform. This form is then placed in a closed chamber to which a sufficientamount of saturated steam is admitted to elevate the temperature quicklyto C. and to maintain it at that temperature thereafter. After fiveminutes treatment, in this chamber at 100 C. the stocking is removed,allowed to cool, withdrawn from the form and subjected to the normaloperations.

of scouring, dyeing, rinsing, finishing (with splash-proof finish),wringing, and reboarding.

Example II The yarns used are:

50 denier20 filament7 turn Z t\vistdull 75 denier30 filament7 turn Ztwist-dull denier--50 filament7 turn 2 twist-dull The yarns are conedafter twisting and are knitted without further treatment into a fabricof predetermined size. The operations of looping and seaming are normaland the stocking is exposed on a boarding form in a steam chamber as inExample I, but using only suflicient steam to elevate the temperature to95 C. After 15 minutes exposure to this hot, wet treatment, the stockingis removed from the form and then scoured, dyed, finished, wrung, andreboarded in the normal manner.

Example III Yarns of the following constructions are prepared:

l8 denier-10 filament7 turn Z twist-dull 75 denier--30 filament-7 turn Ztwist-dull 125 denier50 filament- 1 turn 2 twistdull The twist of the 18denier yarn is increased to 40 turns Z, and two ends of this yarn arethen plied with 26 turns 8 twis to form the yarn for knitting the legand instep. The 75 denier yarn is used for the welt and splice, and the125 denier yarn is used for the toe.

The stocking is knit wet with a single carrier,

.looped and seamed normally. It is then placed on a stocking form andsubjected to the action of boiling water for 5 minutes. It is thenremoved from the form and subjected to the normal scouring, dyeing,finishing, wringing, and reboarding operations.

Example IV Yarn is prepared in the following constructions:

30 denier-10 filament-25 turn 2 t\vistdull 69 denier23 filament-10 turn2 twistdull denier45 filament-10 turn 2 t\vlstdull The 30 denier yarn isused for leg and instep, the 69 denier yarn for splice and welt, and the135 denier yarn for the toe. The liveliness of the twist is removed asin Example I and the yarns ill are knit with a single carrier, loopedand seamed normally. The stocking is then placed on a form and exposedto saturated steam under pressure at 105 C. After the stock and formhave reached the temperature of the steam, they are maintained at thistemperature for 2 minutes. The stocking is then removed from the formand subjected to normal scouring, dyeing, finishing,

wringing, and reboarding operations.

Example V The yarn used in this stocking is 160 denier-60 filament--7turn 2 twist-bright. It is cohed directly after twisting without furthertreatment and is knit on the machines normally used for the preparationof men's half hose, giving a ribbed top and plain leg. Cottonyarn isused for the heel, welt and toe. The stocking is then placed on asuitable boarding form and is subjected to treatment with hot water at96 for 15 minutes. The stocking is then boiled-off, dyed, finished andreboarded in the normal manner.

Example VI Yarn is prepared of the following counts:

denier-15 filament20 turn 2 twist-dull 69 denier-23 filament10 turn 2twistdull 135 (lenier45 filament-10 turn 2 twlstdull This yarn is coned,following twisting, without further treatment, and is knit dry on acircular knitting machine of the type commonly used for the productionof seamless hosiery, using the 45 denier yarn for the leg, the 69 denieryarn for the welt; sole, and heel, and the 135 denier yarn for the toe.The stocking is then placed on a boarding form of essentially the sameshape used for full fashioned hosiery and is exposed to steam under theconditions described in Example II. The completed stocking is thenremoved from the form, scoured, dyed, finished, wrung and reboardecl. Bymeans of the setting in the shape of the boarding form produced in thepreboarding operation a circular knit stocking is obtained which has apermanent shape similar to that of a full fashioned knit stocking andthis shape is not lost when the stocking is washed; The stocking hadremarkable elastic and clinging properties, returning to its boardedshape after distortion.

Although the examples described in this invention have reference tostockings knitted from polyhexamethylene adipamide, it is to beunderstood that it is not to be so limited. The invention is applicableto stockings made from other synthetic linear condensation polyamides,interpolyamides, or mixtures of polyamides. As additional examples ofsuch polyamides might be mentioned polytetramethylene sebacamide,polypentamethylene adipamide, polypentamethylene sebacamide,polyhexamethylene suberamide, polyhexamethylene sebacamide,polyxylylenesebacamide, polymerized G-amino-caproic acid, and polymerized9-aminononanoic acid. There may also be used modified polyamides such asthose derived from the condensation polymerization of polyamide-formingreactants containing another bifunctional reactant, such as a glycol orhydroxy acid. As examples of such polyamides might be mentioned thosederived from a mixture of diamine, dibasic acid, and glycol, or thosederived from a mixture of amino acid and hydroxy acid. The variouspolyamides referred to in this paragraph are all included under the termsynthetic linear condensation polyamide. By the term linear condensationpolyamide I mean to designate polyamide compounds of the types hereindisclosed and their equivalents, whether or not such compounds areproduced by chemical condensation or by some other process.

In making polyamide stockings according to the process of thisinvention, it is preferred to use yarn which has not been subjected toany hot, wet shrinkage treatment which has a strong setting effect onthe yarn. This does not mean that the invention is restricted to the useof unshrunk yarns. Yarns which have beenv shrunk by processes which donot set the yarn with respect to the subsequent board setting step canbe used. A suitable shrinkage treatment of this type consists inexposing the yarn to a dry temperature of about 150 C.'for a short timein a condition which allows it to decrease in length.

It will be understood that the stocking can be made from single yarns oryarns of any desired denier and filament count at any twist; or thatseveral threads can be plied and twisted in the usual way. It ispreferred to use a yarn the twist of which has not\been set by a drasticsetting process for reasons similar to those given above. However, mildtreatments to reduce the liveliness of the twist which do not set theyarn are desirable. This may be done conveniently as illustrated inExample I or by the application of a suitable size or finish.

It will also be understood, of course, that the threads or yarns may becoated with a finish or size in any manner suitable for the textileoperations to be employed. It is sometimes advantageous to lubricatethem by the addition of a suitable oily substance such as a sulfonatedoil, sulfated alcohol, soap and paraffin oil, or with similar\ soaplikematerials. Sizing compositions such a; a mixture of glue and sulfonatedolive oil ma also be used. Hygroscopic materials, such as glycol,diethylene glycol, glycerin, etc., may also be used. It has been foundthat water is a very efiective softener. At least, wet yarns knit morereadily than dry yarns.

It has been indicated in the examples that bright yarns or delusteredyarns may be used. Various materials may be used as delusterants, e. g.,titanium dioxide. Yarns containing any of several modifiers as may bedesired for different purposes may also be used. Although it isgenerally desirable to prepare the stocking from yarns derived fromstraight, continuous polyamide filaments, it is within the scope of theinvention to prepare the stocking from yarns consisting of crimpedpolyamide filaments. Staple fibers, whether straight or crimped, canalso be used in making the stocking. It is also within the scope of theinvention to use yarns containing in addition to polyamide filamentssome silk, wool, cotton, or artificial fibers. The preferred stockings,however, are made entirely of synthetic polyamide filaments.

While it is preferred to knit the stockings on a full-fashioned hosierymachine with a single carrier, it is clear that several carriers or acircular knitting machine may also be used, as is well understood in theart. Since the polyamide yarns are very strong and elastic, a very tightknitting under considerable tension may be used, if desired, and a verydense knitted structure produced.

While it is normally preferred to use a boarding form of the same sizeand shape for both pre-boarding and after-boarding, it has been foundfor certain purposes where a stocking of extreme extensibility isdesired that the preboarding operation can be carried out on a formportion unchanged.

somewhat smaller than that used for the after boarding. For example, theform used for the pro-boarding may be uniformly reduced in its di-'mensions from 2.5% to 10%.

If, however, increased extensibility of only the leg is desired, then itis necessary to reduce only the dimensions of the leg portion of theform leaving the foot Reductions of 2.5% to in dimensions are especiallydesirable.

While the examples illustrate the use of hot water or saturated steam assetting agents in the board setting operation, this invention is not solimited. Instead of water or steam, other liquids may be'used which havea mild swelling action on the filaments under the conditions employed.Hydroxylated non-solvents for. the polyamides are particularly useful assetting agents. Examples of such substances are methanol, ethanol,propanol, and isopropanol. Aniline can also be used as a setting agent.-Mixtures comprising one or more of these substances with or withoutwater may also be used. The temperature and period of exposure necessaryto set the thread will vary depending upon a number of factors includingthe substances used and the yarn employed.

Although the examples have illustrated the use of boarding formsinitially at room temperature, pre-heated forms may be used tov raisemore quickly the temperature of the boarded stocking to thetemperature,of its surroundings. Forms heated from the interior by means of gas,electricity, steam, etc., to expedite the, boarding operation may alsobe used. Similarly, the boarding form may be perforated to permit theegress of hot or cold water and/or steam or other setting agents to wetthe boarded stocking or to maintain it in a hot, wet atmosphere.

- For convenience, the manufacture of stockings has been discussed. Itwill be understood that this invention is equally applicable to themanufacture of knitted structures generally wherein a finishing orafter-treatment comparable to that used in making stockings is appliedto the knittedstructure.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not to be limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

'1. The process of fabricating knitted goods containing synthetic linearcondensation polyamide fibers which comprises knitting yarns com prisingsaid fibers, pre-boarding the knitted goods, thereafter subjecting thegoods to a hot liquid treatment, then re-boarding the goods whereby toimpart to the goods a smooth, wrinkle free appearance.

2. The process of fabricating hosiery containing synthetic .linearcondensation polyamide fibers which comprises forming hosiery from yarncomprising said fibers, pre-boarding the hosiery, thereafter subjectingthe hosiery to a hot liquid treatment, then re-boarding the hosierywhereby to impart to the hosiery a smooth, wrinkle free appearance.

3. The process of fabricating hosiery contain ingsynthetic linearcondensation polyamide fibers which comprises forming full-fashionedhosiery from yarn comprising said fibers, pre boarding the hosiery,thereafter subjecting the hosiery to a hot liquid treatment, thenre-boarding the hosiery whereby to impart to the hosiery a smooth,wrinkle free appearance.

4. The process of fabricating hosiery containing synthetic linearcondensation polyamide fibers which comprises forming hosiery from yarncomprising said fibers, pre-boarding the hosiery, thereafter dyeing thehosiery by contact with a hot dyeing solution, then re-boarding thehosiery whereby to impart to the hosiery a smooth, wrinkle freeappearance 5. The process which .comprises fabricating hosierycomprising synthetic linear condensation polyamide fibers whichcomprises knitting yarn comprisingsaid fibers, forming, full-fashionedhosiery fromthe knitted goods so formed, subjecting the hosiery to apro-boarding operation, scouring and dyeing said hosiery, thensubjecting the hosiery to a re-boarding operation whereby polyamidefibers which comprises knitting yarn comprising said fibers, formingfull-fashioned hosiery from the knitted goods so formed, subjecting thehosiery to a pro-boarding operation,

' scouring, dyeingfinishing and wringing said hosiery, then subjectingthe hosieryto a re-boarding operation whereby to impart thereto a smoothunwrinkled appearance. i v

'JOHNBLANCHARD JR.

